August 12, 1887.] 



SCIENCE. 



79 



his head visible. At two hundred yards the dog detected her 

 master, and went to him directly. 



From these tests, Dr. Romanes concludes that the dog distin- 

 guishes him from all others by the odor of his boots (i -6), and 

 does not distinguish him in his naked feet (8-11). The odor is 

 probably emitted by the feet, but must be mixed with that of shoe- 

 leather to be of service to the dog. This is doubtless a matter of 

 ■education ; had the dog been used to following her master when 

 without shoes, the animal would have learned to follow him thus. 

 The characteristic odor cannot penetrate a sheet of brown paper, 

 but a few square millimetres of surface is sufficient to give the dog 

 the clew. The animal is ready to be guided by inference as well 

 as by perception, but the inference is instantaneous (12 and 13 as 

 compared with 2, 8, and 11). Lastly, not only the feet (through 

 the boots) but the whole body emits an odor that the dog can dis- 

 tinguish in a mass of others (15). This order is recognized at 

 great distances to windward (15), or in calm weather in any direc- 

 tion (16) : it is not overpowered by anise-seed-oil (14) or by the foot- 

 prints of another (4). 



The Time Necessary to perceive Cold and Heat. — It is 

 well known that a cold sensation reaches consciousness more 

 rapidly than a sensation of warmth. Dr. Goldscheider of Berlin, 

 whose researches on the hot and cold points of the skin have 

 gained him a well-deserved reputation, has recently accurately 

 measured the length of the time necessary to perceive these sensa- 

 tions. The observations were made on parts equally sensitive to 

 heat and cold, and with intensities of heat and cold equally differ- 

 ent from the temperature of the part. The time of contact was 

 recorded electrically by means of a metallic button fixed to the skin. 

 Contact with a cold point was felt on the face after 13.5, on the arm 

 after 18, on the abdomen after 22, on the knee after 25, hun- 

 dredths of a second. The sensation of a hot point was felt on the 

 same surfaces after 19, 27, 62, and 79 hundredths of a second re- 

 spectively. This great difference in time has an important theo- 

 retical bearing on the physiology of dermal sensations. 



BOOK -REVIEWS. 



Geological History of Lake Lahontan, a Quaternary Lake of 

 North-western Nevada. (U.S. Geol. Surv., Monogr. XI.) 

 By I. C. Russell. Washington, Government. 4". 



This volume, and the companion monograph by Gilbert on 

 Lake Bonneville, are undoubtedly among the most interesting, if 

 not the most important, contributions hitherto made to the ancient 

 geography of this continent. It must be admitted, however, that 

 the wonderful changes in the aspect of the Great Basin, of which 

 we find here the most conclusive evidence, are scarcely ancient in 

 the geological sense, having been accomplished almost wholly 

 since the close of the glacial epoch, and largely since the advent of 

 man. 



Lake Lahontan, situated mostly within the area now forming the 

 State of Nevada, filled a depression along the western border of 

 the Great Basin, at the base of the Sierra Nevada; while Lake 

 Bonneville, embraced almost entirely in the present Territory of 

 Utah, occupied a corresponding position on the east side of the 

 Great Basin, at the foot of the Wasatch Mountains. 



The hydrographic basins of these two water-bodies embraced the 

 entire width of the Great Basin in latitude 41°. Lake Bonneville 

 was 19,750 square miles in area, and had a maximum depth of about 

 1,000 feet. Lake Lahontan covered 8,422 square miles of surface, 

 and in the deepest part, the present site of Pyramid Lake, was 866 

 feet in depth. The ancient lake of Utah overflowed northward, 

 and cut down its channel of discharge 370 feet. The ancient lake 

 of Nevada did not overflow. Each of these lakes had two high- 

 water stages, separated by a time of desiccation. In the Lahontan 

 basin, as in the Bonneville, the first great rise was preceded by 

 a long period of desiccation, and was followed by a second 

 dry epoch, during which the valleys of Nevada were even more 

 completely desert than at present. During the second flood-stage, 

 the lake rose higher than at the time of the first high water, and 

 then evaporated to complete desiccation ; for the present lakes of 

 the basin (Pyamid, Winnemucca, etc.) are of comparatively recent 

 date, and are nearly fresh, for the reason that the salts deposited 



when the quaternary lake evaporated were buried or absorbed by 

 the clays and marls that occupy the bottom of the basin. 



As Lake Lahontan did not overflow, it became the receptacle for 

 all the mineral matter supplied by tributary streams and springs, 

 both in suspension and in solution. The former was deposited as 

 lacustral sediments, and the latter as calcareous tufa, or formed 

 desiccation products when the lake evaporated. 



The introductory chapter contains a sketch of the Great Basin as 

 the explorer finds it to-day. It stands in marked contrast in nearly 

 all its scenic features with the remaining portions of the United 

 States. The traveller in this region is no longer surrounded by the 

 open, grassy parks and heavily timbered mountains of the Pacific 

 slope, or by the rounded and flowing outlines of the forest-crowned 

 Appalachians ; and the scenery suggests nought of the boundless 

 plains east of the Rocky Mountains or of the rich savannas of the 

 Gulf States. He must compare it, rather, to the parched and 

 desert areas of Arabia and the shores of the Dead Sea or the 

 Caspian. 



To the geographer the most striking characteristic of the country 

 stretching eastward from the base of the Sierra Nevada to the 

 Rocky Mountain system is that it is a region of interior drainage. 

 For this reason it is known as the ' Great Basin.' No streams that 

 rise within it carry their contributions to the ocean ; and the climate 

 is dry in the extreme, the average yearly precipitation not exceeding 

 twelve or fifteen inches. 



The area thus isolated from oceanic water-systems is 800 miles 

 in length from north to south, and nearly 500 miles broad, and con- 

 tains about 208,500 square miles. At the south the valleys of the 

 Great Basin are low-lying. Death Valley and the Colorado Desert 

 being depressed below the level of the sea ; but at the north the 

 valleys have a general elevation of from 4,000 to 5,000 feet, while 

 the intervening mountain-ranges rise from 5,000 to 7,000 feet above 

 them. 



The mountains exhibit a type of structure not described before 

 this region was explored, but now recognized by geologists as the 

 ' Basin Range structure.' They are long, narrow ridges, usually 

 bearing nearly north and south, steep upon one side, where the 

 broken edges of the strata are exposed, but sloping on the other 

 with a gentle angle conformable to the dip of the beds. They 

 have been formed by the orographic tilting of blocks of the earth's 

 crust, that are separated by profound faults, and they do not exhibit 

 the anticlinal and synclinal structures commonly observed in moun- 

 tains, but are monoclinal instead. The mountains are rugged and 

 angular, usually unclothed by vegetation, and owe their marvel- 

 lously rich colors to the rocks of which they are composed, 

 especially the purple trachytes, the deep-colored rhyolites, and the 

 many-hued volcanic tuffs so common in western Nevada, often 

 rivalling the brilliant tints of the New England hills in autumn. 



The valleys or plains separating the mountain-ranges, far from 

 being fruitful, shady vales, with life-giving streams, are often ab- 

 solute deserts, totally destitute of water, and treeless for many 

 days' journey, the gray-green sagebrush alone giving character to 

 the landscape. Many of them have playas in their lowest depres- 

 sions (simple mud-plains left by the evaporation of former lakes) 

 that are sometimes of vast extent. In the desert bordering Great 

 Salt Lake on the west, and in the Black Rock Desert of northern 

 Nevada, are tracts hundreds of square miles in area showing 

 scarcely a trace of vegetation. In winter, portions of these areas 

 are occupied by shallow lakes, but during the summer months they 

 become so baked and hardened as scarcely to receive an impres- 

 sion from a horse's hoof, and so sun-cracked as to resemble tessel- 

 lated pavements of cream-colored marble. Other portions of the 

 valleys become incrusted to the depth of several inches with alka- 

 line salts, which rise to the surface as an efflorescence, and give the 

 appearance of drifting snow. The dry surface material of the 

 deserts is sometimes blown about by the wind, saturating the air 

 with alkaline particles, or is caught up by whirlwinds and carried 

 to a great height, forming hollow columns of dust. These swaying 

 and bending columns, often two or three thousand feet high, rising 

 from the plains like pillars of smoke, form a characteristic feature 

 of the deserts. 



Chapter II., on the genesis of Lake Lahontan, contains a sum- 

 mary of the facts which show that the lake filled a compound 



